The invention relates to radiation-sensitive positively acting materials for ultraviolet, electron or X-ray beam lithography on the basis of linear non-crosslinked polymer acrylic acid or methacrylic acid derivatives having side chains of different length.
Radiation-sensitive materials are generally high-molecular polymer organic compounds having average molecular weights of approximately 5.multidot.10.sup.3 to 5.multidot.10.sup.6, which compounds change their solubility properties with respect to specific solvents under the action of energy-rich radiation. Positively acting materials are depolymerized by energy-rich radiation and thus are more soluble, whereas negatively acting materials are crosslinked and therefore less easily soluble.
The lowest possible radiation dose which is necessary for depolymerization or crosslinking of a material with a certain layer thickness gives the sensitivity of the respective material.
These compounds designated as resistant materials are preferably used as etching masks for producing microstructures of high resolution in semiconductor technology.
Positively acting resistant materials on the basis of polymethacrylates are known and are described by J. Haller et al (IBM Journal Res. 12. 251, 1968) and others. Similarly copolymers of methacrylic acid esters having organic acids or chlorides containing polymerizable double bonds are known and these are quasi cross-linked by treatment with water-vapour-enriched nitrogen by forming acid anhydride groups and are depolymerized by means of energy-rich radiation, c.f. German Offenlegungsschrift Nos. 23 63 092 and 26 10 301.
By crosslinking and subsequently depolymerizing the copolymers described in German Offenlengungsschrift No. 26 10 301, a sensitivity of 30-60/uC/cm.sup.2 is said to be achieved, this sensitivity being relatively low in comparison with comparable values of other known resistant materials. These other known materials do however have other disadvantages such as adhesive problems for example and lower resistance to etching in different media such as for example when structuring aluminum substrates.